linux-kernel - [PATCH v2 02/20] xen: Introduce a function to split a Linux page into Xen page

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Date:	Thu, 9 Jul 2015 21:42:14 +0100
From:	Julien Grall <julien.grall@...rix.com>
To:	<xen-devel@...ts.xenproject.org>
CC:	<linux-arm-kernel@...ts.infradead.org>, <ian.campbell@...rix.com>,
	<stefano.stabellini@...citrix.com>, <linux-kernel@...r.kernel.org>,
	"Julien Grall" <julien.grall@...rix.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	David Vrabel <david.vrabel@...rix.com>
Subject: [PATCH v2 02/20] xen: Introduce a function to split a Linux page into Xen page

The Xen interface is always using 4KB page. This means that a Linux page
may be split across multiple Xen page when the page granularity is not
the same.

This helper will break down a Linux page into 4KB chunk and call the
helper on each of them.

Signed-off-by: Julien Grall <julien.grall@...rix.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc: David Vrabel <david.vrabel@...rix.com>
---
    Changes in v2:
        - Patch added
---
 include/xen/page.h | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/include/xen/page.h b/include/xen/page.h
index 8ebd37b..b1f7722 100644
--- a/include/xen/page.h
+++ b/include/xen/page.h
@@ -39,4 +39,24 @@ struct xen_memory_region xen_extra_mem[XEN_EXTRA_MEM_MAX_REGIONS];
 
 extern unsigned long xen_released_pages;
 
+typedef int (*xen_pfn_fn_t)(struct page *page, unsigned long pfn, void *data);
+
+/* Break down the page in 4KB granularity and call fn foreach xen pfn */
+static inline int xen_apply_to_page(struct page *page, xen_pfn_fn_t fn,
+				    void *data)
+{
+	unsigned long pfn = xen_page_to_pfn(page);
+	int i;
+	int ret;
+
+	for (i = 0; i < XEN_PFN_PER_PAGE; i++, pfn++) {
+		ret = fn(page, pfn, data);
+		if (ret)
+			return ret;
+	}
+
+	return ret;
+}
+
+
 #endif	/* _XEN_PAGE_H */
-- 
2.1.4

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